I2C

The I2C bus was designed by Philips in the early ’80s to allow easy communication
between components which reside on the same circuit board. Philips Semiconductors
migrated to NXP in 2006.

The name I2C translates into “Inter IC”. Sometimes the bus is called IIC or I²C bus.
There are two wires, SDA and SCL.

The first thing to realize: SDA and SCL are open-drain (also known as open-collector
in the TTL world), that is I2C master and slave devices can only drive these lines
low or leave them open

It has a 7 bit addressing scheme (along with a rarely used 10 bit scheme).
Transmissions are done in 8 byte bursts, which the first byte of the transmissing
being an address and a 1 bit read or write flag.